Danish Cord Seat - #2 Shaping & Mortising the Legs

First parts to be made are the legs.  I started on them because they have quite a few mortises and it is my procedure to make the mortises first then fit the tenons that go in them second.  I do it in that order because the mortises are made on the mortising machine which uses a fixed width chisel/bit combination.  The tenons on the other hand are cut on the table saw making their finished size adjustable.  Anyway, it all begins by printing out a full-size pattern of the upper part of the leg and gluing it to a piece of ¼” plywood.  That’s shown below along with the leg blank.

The straight part of the pattern is cut on the table saw while the curved part is cut with the jig saw using a ground fine tooth blade.  The table saw cut is right at the finished width while the jig sawn part is cut slightly wide of the line to allow for a smooth curve and transition into the straight part.  Here the straight cut is done and a little bit of the curved cut has been made with the jig saw.

Next using the oscillating drum sander, the jig sawn cut is smoothed and blended into the straight table saw cut.  I start with a coarse sanding sleeve then use a fine grit sleeve.  That’s followed by some hand sanding to completely blend things together.

Layout of the curve on the legs along with all the mortises is next.  The legs are not all the same, there are mirrored pairs.  Here you can see how the they will be arranged.  Note the labels, LF for Left Front, RF for Right Front and so on as to which one goes where.

Cutting the straight part of the legs comes next and that’s done on the table saw with a stop to keep me from cutting too far along the line and getting into the curved area.  While it looks like the cut could be continued that’s deceiving since the bottom of the blade cuts farther than the exposed part.  The blue tape is there to give me a good place to grab when pulling the leg back out.

After the straight cut it’s over to the bandsaw to rough out the curve.

Fairing the bandsawn curved edge and the table saw cut straight section together is next.  That’s done using the same process as when the template was made.  The top photo has the finished blended edge completed on top with the bottom showing what it looks like right off the bandsaw.  The bottom photo is a closer look.

Cutting the mortises in the leg is next.  I use a dedicated mortise machine to make them.  It uses mortising bits comprised of a square hollow chisel that squares the edges and a special drill bit that leads the hollow chisel cut and removes wood shavings all mounted in a powered head.  A long handle gives the mechanical advantage for plunging the cut.  In use the piece to have the mortise drilled is clamped to a table that moves front to back and side to side.  The side to side movement can be limited with stops for making identical repeating cuts.  Depth of cut is controlled with a stop on the head.  When my son was young, I bet him that I could drill square holes.  He didn’t believe me and thought it was impossible.  When I took him into the shop and made a couple the look on his face was priceless.

Here is what the setup looks like with the ends done.  They are cut first so there is even lateral pressure on all sides of the bit.  If one side is open the bit could drift throwing the mortise out of square.

This is what the finished mortise looks like.

Since the legs are mirrored pairs two different setups are required.  This is what the second setup looks like.  All the measurements and process are the same just reversed. 

For the next set of mortises the layout starts on a test piece using a dial caliper and marking knife.  Because a knife mark is hard for me to clearly see on light wood like oak chalk is rubbed into the cuts making them readily visible.  In the bottom photo the right mortise is easy to see while the one on the left is not so visible.

To make sure the chisel is aligned with the layout lines the end of a small steel square is set against the chisel/bit set and the table moved in or out until they are aligned.  The side to side adjustment follows the same process except that when aligned at the ends the stops are locked in place.  Once set up you can easily make two or fifty identical pieces.

Once a test piece is cut and all the measurements check out there is one last step before cutting the second set of mortises.  A filler plug is needed where two of the mortises will intersect.   The plug is made out of scrap oak sized so it fits snugly in the mortise.  The reason the plug is needed is to prevent a blowout in the first mortise when the second one is cut and punches through the side of the first one.  The top drawing shows the intersection highlighted in red and the bottom photo shows the filler plug in place. 

With the plug is in place the remaining mortises can be cut being sure to remember to make mirrored pairs.  After these mortises are cut the plugs can be removed and discarded.  Here are what the four legs look like with all the mortises cut.

Next Up – Cutting Tenons & Routing